unused_parens incorrectly lints on `if let true = (false && true) {}`

[Centril]

warning: unnecessary parentheses around `if let` head expression
 --> src/lib.rs:2:19
  |
2 |     if let true = (false && true) {}
  |                   ^^^^^^^^^^^^^^^ help: remove these parentheses
  |
  = note: #[warn(unused_parens)] on by default

If we remove the parens we correctly get:

error: ambiguous use of `&&`
 --> src/lib.rs:2:19
  |
2 |     if let true = false && true {}
  |                   ^^^^^^^^^^^^^ help: consider adding parentheses: `(false && true)`
  |
  = note: this will be a error until the `let_chains` feature is stabilized
  = note: see rust-lang/rust#53668 for more information

cc #53667 #53668

The lint should take let_chains into account.

[Centril]

This is a rather obscure bug which no one seems to have hit thus far... I only found it due to working on let_chains. I'll fix the issue as part of this work.